The present invention relates to coiled tubing handling equipment for use in drilling, production, and servicing of wells used for production of petroleum products. The invention is used on wheel type coiled tubing injectors that are used to insert and withdraw coiled tubing from wells.
When continuous coiled tubing is to be used in a well as a service tubing string, a production string, or a drill string, it must be taken from a reel, forced into the well, manipulated, withdrawn from the well, and stored back on its reel. Generally the well is either under or potentially under some pressure, so that the friction of a sealing gland or blowout preventer at the top of the wellhead must be overcome. Further, well pressure may strongly resist insertion of the tubing into the well. While the tubing is being recovered from the well, the weight of the tubing must be lifted from the well. Additionally, there may be substantial friction between the coiled tubing and the well tubing or casing to be overcome while the coiled tubing is in the well, particularly if the well is deviated from vertical. For these reasons, means have been developed to apply axial thrusts to the string of coiled tubing at the wellhead. These means are commonly termed coiled tubing injectors in the oilfield industry.
Two basic types of coiled tubing injector are used. The first and most common type consists of opposed tracks analogous to the tracks on a crawler tractor, which clamp and thereby grip the tubing between the tracks so that the tracks can transmit axial loadings into the tubing by friction. This track-type type of injector is manufactured and sold by Hydra-Rig, Inc. and others. U.S. Pat. Nos. 3,258,110, 5,188,174, 5,309,990, and 5,975,203 show track-type injectors.
The second type of tubing injector uses a wheel with opposed pinch rollers, which force the tubing against the rim of the wheel. When torque is applied to the wheel, frictional shear forces cause axial loads to be transmitted to the tubing. This wheel-type of injector is manufactured and sold by Coiled Tubing Systems and Vita International, Inc. U.S. Pat. Nos. 4,673,035 and 5,765,643 show examples of this type of injector system.
A serious problem, which arises with the use of coiled tubing for both types of tubing injectors is related to progressive cross-sectional ovaling as a consequence of repeated bending beyond the yield point of the tubing material. This undesirable effect may be minimized, given that other design factors are constant, by providing grooved contact surfaces, which closely conform to the tubing diameter.
U.S. Pat. Nos. 3,754,474, 5,094,340, 5,853,118, and 6,189,609 show means for supporting the tubing for track-type injectors. Initially, some designers used separate sets of drive chain-mounted blocks for each tubing size, each set being grooved specifically to fit a given tubing size. U.S. Pat. No. 3,754,373 relies upon an elastomeric pad with embedded gripper studs on the face of the individual drive chain-mounted blocks. For this configuration, the elastomer deforms to accommodate the particular tubing which it contacts. U.S. Pat. Nos. 5,094,340 and 5,853,118 use a Vee groove block which reduces the cross-sectional bending stresses relative to those of a single contact line block by providing two lines of contact approximately 90xc2x0 apart. The advantage of a Vee groove block is that the block can be used with a wide range of tubing sizes. However, if high transverse squeeze is used to enhance the frictional transfer of drive force from the drive chain-mounted blocks to the tubing, excessive ovaling may occur with Vee grooves. Shaaban et al. in U.S. Pat. No. 6,189,609 B1 shows an insertable gripper block made of resilient material for use with composite coiled tubing fabricated from plastics and reinforcing fibers. This particular arrangement has the gripper block material selected for its high friction against the tubing and its relatively less aggressive wear tendencies when contacting the soft tubing.
Gipson in U.S. Pat. No. 4,673,035 discloses a wheel-type injector, which uses a permanent rubber insert on the wheel perimeter to support the tubing. As configured, the system would possibly require a different wheel for at least some of the currently available coiled tubing sizes and the rubber insert on the wheel perimeter is subject to wear.
For track-type coiled tubing injectors, the changing of the blocks that will contact the tubing is expensive due to the amount of equipment down time required. For wheel-type injectors, the interchange of drive wheels to accommodate different tubing sizes is also very time consuming and additionally requires lifting equipment. However, larger coiled tubing with its more severe bending cycles and higher squeeze loads coupled with higher radial loads from increased tension for wheel-type injectors in the injector necessitate better cross-sectional support for the tubing.
While operational time savings are important for operators of wheel-type injectors, weight reduction for the overall system is also important for reducing operating costs and permitting larger tubing loads with the rig. Coiled tubing rig weights are limited by regulations on vehicle weight and bridge load capacities. The use of light weight alloys, such as aluminum, for the relatively large rim portion of a wheel-type injector would appear advantageous, but the very poor wear properties of aluminum and other light metals preclude their use for pipe contact. The portion of the wheel system which contacts the tubing must be able to resist wear while offering good frictional properties even when the tubing has residual water, drilling mud, or petroleum products on its surface.
Thus, a need exists for a wheel system for wheel-type coiled tubing injectors that have a light weight, robust, and wear resistant means of contacting and fully supporting the tubing while, at the same time, offering the advantages of quick adaptation for other sizes of tubing.
The foregoing has outlined rather broadly several aspects of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter which form the subject of the claims of the invention. It should be appreciated by those skilled in the art that the conception and the specific embodiment disclosed might be readily utilized as a basis for modifying or redesigning the structures for carrying out the same purposes as the invention. It should be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the appended claims.
The invention contemplates a simple, inexpensive device for solving the problems and disadvantages of the prior approaches discussed above. The present invention includes an interchangeable coil tubing support block that provides a means for quickly adapting a wheel system for wheel-type coiled tubing injectors for a wide variety of tubing sizes.
In accordance with one aspect of the invention is a drive wheel assembly for use in a wheel-type coiled tubing injector comprising: a drive wheel with a concentric axis of rotation and a rim having an annular groove; a number of carrier blocks having an upper side and a lower side, where the lower side is attached to the annular groove of the rim of the drive wheel; and a number of insert blocks, where each insert block has a first side selectably securable to the upper side of a corresponding carrier block and an opposed side having an arcuate surface for supporting a portion of coiled tubing in contact with the arcuate surface.
In accordance with another aspect of the invention is a drive wheel assembly for use in a wheel-type coiled tubing injector comprising: a drive wheel having a concentric axis of rotation and a rim having an annular groove; a carrier block having a stepped flat on a lower side, the stepped flat mates with the groove of the rim of the drive wheel, and an upper side comprising a semicylindrical groove along a length of the upper side, said semicylindrical groove has a transverse shouldering groove approximately midway along the length of the upper side of the carrier block, wherein multiple carrier blocks form a continuous array around the circumference of the rim; an insert block having a semicylindrical exterior that mates with the semicylindrical groove of the carrier block, said semicylindrical exterior having a central upset portion that fits into the shouldering groove of the carrier block, and an arcuate interior for supporting a portion of a coiled tubing, wherein the radius of the arcuate interior is selected to correspond to the radius of the coiled tubing to be supported by the arcuate interior; and an attachment element for reversibly attaching the insert block to the carrier block.